POPA/POPAD

Pop All General-Purpose Registers

Opcodes

Hex Mnemonic Encoding Long Mode Legacy Mode Description
61 POPAD A Invalid Valid Pop EDI, ESI, EBP, EBX, EDX, ECX, and EAX.
61 POPA A Invalid Valid Pop DI, SI, BP, BX, DX, CX, and AX.

Instruction Operand Encoding

Op/En Operand 0 Operand 1 Operand 2 Operand 3
A NA NA NA NA

Description

Pops doublewords (POPAD) or words (POPA) from the stack into the general-purpose registers. The registers are loaded in the following order: EDI, ESI, EBP, EBX, EDX, ECX, and EAX (if the operand-size attribute is 32) and DI, SI, BP, BX, DX, CX, and AX (if the operand-size attribute is 16). (These instructions reverse the operation of the PUSHA/PUSHAD instructions.) The value on the stack for the ESP or SP register is ignored. Instead, the ESP or SP register is incremented after each register is loaded.

The POPA (pop all) and POPAD (pop all double) mnemonics reference the same opcode. The POPA instruction is intended for use when the operand-size attribute is 16 and the POPAD instruction for when the operand-size attribute is 32. Some assemblers may force the operand size to 16 when POPA is used and to 32 when POPAD is used (using the operand-size override prefix [66H] if necessary). Others may treat these mnemonics as synonyms (POPA/POPAD) and use the current setting of the operand-size attribute to determine the size of values to be popped from the stack, regardless of the mnemonic used. (The D flag in the current code segment's segment descriptor determines the operand-size attribute.)

This instruction executes as described in non-64-bit modes. It is not valid in 64-bit mode.

Pseudo Code

IF 64-Bit Mode
	#UD;
ELSE
	IF OperandSize = 32 (* Instruction = POPAD *)
		EDI = Pop();
		ESI = Pop();
		EBP = Pop();
		Increment ESP by 4; (* Skip next 4 bytes of stack *)
		EBX = Pop();
		EDX = Pop();
		ECX = Pop();
		EAX = Pop();
	ELSE
		(* OperandSize = 16, instruction = POPA *)
		DI = Pop();
		SI = Pop();
		BP = Pop();
		Increment ESP by 2; (* Skip next 2 bytes of stack *)
		BX = Pop();
		DX = Pop();
		CX = Pop();
		AX = Pop();
	FI;
FI;

Flags Affected

None.

Exceptions

64-Bit Mode Exceptions

Exception Description
#UD If in 64-bit mode.

Compatibility Mode Exceptions

Same as for protected mode exceptions.

Virtual-8086 Mode Exceptions

Exception Description
#UD If the LOCK prefix is used.
#AC(0) If an unaligned memory reference is made while alignment checking is enabled.
#PF(fault-code) If a page fault occurs.
#SS(0) If the starting or ending stack address is not within the stack segment.

Real-Address Mode Exceptions

Exception Description
#UD If the LOCK prefix is used.
#SS If the starting or ending stack address is not within the stack segment.

Protected Mode Exceptions

Exception Description
#UD If the LOCK prefix is used.
#AC(0) If an unaligned memory reference is made while the current privilege level is 3 and alignment checking is enabled.
#PF(fault-code) If a page fault occurs.
#SS(0) If the starting or ending stack address is not within the stack segment.